Commit 48cca7e4 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

libbpf: add support for bpf_call 



- recognize relocation emitted by llvm
- since all regular function will be kept in .text section and llvm
  takes care of pc-relative offsets in bpf_call instruction
  simply copy all of .text to relevant program section while adjusting
  bpf_call instructions in program section to point to newly copied
  body of instructions from .text
- do so for all programs in the elf file
- set all programs types to the one passed to bpf_prog_load()

Note for elf files with multiple programs that use different
functions in .text section we need to do 'linker' style logic.
This work is still TBD

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent d98588ce

tools/include/uapi/linux/bpf.h

+6 −0
Original line number Diff line number Diff line
@@ -197,8 +197,14 @@ enum bpf_attach_type { 
 */

#define BPF_F_STRICT_ALIGNMENT	(1U << 0)



/* when bpf_ldimm64->src_reg == BPF_PSEUDO_MAP_FD, bpf_ldimm64->imm == fd */

#define BPF_PSEUDO_MAP_FD	1



/* when bpf_call->src_reg == BPF_PSEUDO_CALL, bpf_call->imm == pc-relative

 * offset to another bpf function

 */

#define BPF_PSEUDO_CALL		1



/* flags for BPF_MAP_UPDATE_ELEM command */

#define BPF_ANY		0 /* create new element or update existing */

#define BPF_NOEXIST	1 /* create new element if it didn't exist */

tools/lib/bpf/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -40,7 +40,7 @@ int bpf_create_map_in_map(enum bpf_map_type map_type, const char *name, 
			  __u32 map_flags);



/* Recommend log buffer size */

#define BPF_LOG_BUF_SIZE 65536

#define BPF_LOG_BUF_SIZE (256 * 1024)

int bpf_load_program_name(enum bpf_prog_type type, const char *name,

			  const struct bpf_insn *insns,

			  size_t insns_cnt, const char *license,

tools/lib/bpf/libbpf.c

+127 −43
Original line number Diff line number Diff line
@@ -174,12 +174,19 @@ struct bpf_program { 
	char *name;

	char *section_name;

	struct bpf_insn *insns;

	size_t insns_cnt;

	size_t insns_cnt, main_prog_cnt;

	enum bpf_prog_type type;



	struct {

	struct reloc_desc {

		enum {

			RELO_LD64,

			RELO_CALL,

		} type;

		int insn_idx;

		union {

			int map_idx;

			int text_off;

		};

	} *reloc_desc;

	int nr_reloc;
@@ -234,6 +241,7 @@ struct bpf_object { 
		} *reloc;

		int nr_reloc;

		int maps_shndx;

		int text_shndx;

	} efile;

	/*

	 * All loaded bpf_object is linked in a list, which is
@@ -375,9 +383,13 @@ bpf_object__init_prog_names(struct bpf_object *obj) 
	size_t pi, si;



	for (pi = 0; pi < obj->nr_programs; pi++) {

		char *name = NULL;

		const char *name = NULL;



		prog = &obj->programs[pi];

		if (prog->idx == obj->efile.text_shndx) {

			name = ".text";

			goto skip_search;

		}



		for (si = 0; si < symbols->d_size / sizeof(GElf_Sym) && !name;

		     si++) {
@@ -405,7 +417,7 @@ bpf_object__init_prog_names(struct bpf_object *obj) 
				   prog->section_name);

			return -EINVAL;

		}



skip_search:

		prog->name = strdup(name);

		if (!prog->name) {

			pr_warning("failed to allocate memory for prog sym %s\n",
@@ -795,6 +807,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj) 
		} else if ((sh.sh_type == SHT_PROGBITS) &&

			   (sh.sh_flags & SHF_EXECINSTR) &&

			   (data->d_size > 0)) {

			if (strcmp(name, ".text") == 0)

				obj->efile.text_shndx = idx;

			err = bpf_object__add_program(obj, data->d_buf,

						      data->d_size, name, idx);

			if (err) {
@@ -856,11 +870,14 @@ bpf_object__find_prog_by_idx(struct bpf_object *obj, int idx) 
}



static int

bpf_program__collect_reloc(struct bpf_program *prog,

			   size_t nr_maps, GElf_Shdr *shdr,

			   Elf_Data *data, Elf_Data *symbols,

			   int maps_shndx, struct bpf_map *maps)

bpf_program__collect_reloc(struct bpf_program *prog, GElf_Shdr *shdr,

			   Elf_Data *data, struct bpf_object *obj)

{

	Elf_Data *symbols = obj->efile.symbols;

	int text_shndx = obj->efile.text_shndx;

	int maps_shndx = obj->efile.maps_shndx;

	struct bpf_map *maps = obj->maps;

	size_t nr_maps = obj->nr_maps;

	int i, nrels;



	pr_debug("collecting relocating info for: '%s'\n",
@@ -893,8 +910,10 @@ bpf_program__collect_reloc(struct bpf_program *prog, 
				   GELF_R_SYM(rel.r_info));

			return -LIBBPF_ERRNO__FORMAT;

		}

		pr_debug("relo for %ld value %ld name %d\n",

			 rel.r_info >> 32, sym.st_value, sym.st_name);



		if (sym.st_shndx != maps_shndx) {

		if (sym.st_shndx != maps_shndx && sym.st_shndx != text_shndx) {

			pr_warning("Program '%s' contains non-map related relo data pointing to section %u\n",

				   prog->section_name, sym.st_shndx);

			return -LIBBPF_ERRNO__RELOC;
@@ -903,6 +922,17 @@ bpf_program__collect_reloc(struct bpf_program *prog, 
		insn_idx = rel.r_offset / sizeof(struct bpf_insn);

		pr_debug("relocation: insn_idx=%u\n", insn_idx);



		if (insns[insn_idx].code == (BPF_JMP | BPF_CALL)) {

			if (insns[insn_idx].src_reg != BPF_PSEUDO_CALL) {

				pr_warning("incorrect bpf_call opcode\n");

				return -LIBBPF_ERRNO__RELOC;

			}

			prog->reloc_desc[i].type = RELO_CALL;

			prog->reloc_desc[i].insn_idx = insn_idx;

			prog->reloc_desc[i].text_off = sym.st_value;

			continue;

		}



		if (insns[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {

			pr_warning("bpf: relocation: invalid relo for insns[%d].code 0x%x\n",

				   insn_idx, insns[insn_idx].code);
@@ -924,6 +954,7 @@ bpf_program__collect_reloc(struct bpf_program *prog, 
			return -LIBBPF_ERRNO__RELOC;

		}



		prog->reloc_desc[i].type = RELO_LD64;

		prog->reloc_desc[i].insn_idx = insn_idx;

		prog->reloc_desc[i].map_idx = map_idx;

	}
@@ -962,17 +993,60 @@ bpf_object__create_maps(struct bpf_object *obj) 
	return 0;

}



static int

bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,

			struct reloc_desc *relo)

{

	struct bpf_insn *insn, *new_insn;

	struct bpf_program *text;

	size_t new_cnt;



	if (relo->type != RELO_CALL)

		return -LIBBPF_ERRNO__RELOC;



	if (prog->idx == obj->efile.text_shndx) {

		pr_warning("relo in .text insn %d into off %d\n",

			   relo->insn_idx, relo->text_off);

		return -LIBBPF_ERRNO__RELOC;

	}



	if (prog->main_prog_cnt == 0) {

		text = bpf_object__find_prog_by_idx(obj, obj->efile.text_shndx);

		if (!text) {

			pr_warning("no .text section found yet relo into text exist\n");

			return -LIBBPF_ERRNO__RELOC;

		}

		new_cnt = prog->insns_cnt + text->insns_cnt;

		new_insn = realloc(prog->insns, new_cnt * sizeof(*insn));

		if (!new_insn) {

			pr_warning("oom in prog realloc\n");

			return -ENOMEM;

		}

		memcpy(new_insn + prog->insns_cnt, text->insns,

		       text->insns_cnt * sizeof(*insn));

		prog->insns = new_insn;

		prog->main_prog_cnt = prog->insns_cnt;

		prog->insns_cnt = new_cnt;

	}

	insn = &prog->insns[relo->insn_idx];

	insn->imm += prog->main_prog_cnt - relo->insn_idx;

	pr_debug("added %zd insn from %s to prog %s\n",

		 text->insns_cnt, text->section_name, prog->section_name);

	return 0;

}



static int

bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj)

{

	int i;

	int i, err;



	if (!prog || !prog->reloc_desc)

		return 0;



	for (i = 0; i < prog->nr_reloc; i++) {

		int insn_idx, map_idx;

		if (prog->reloc_desc[i].type == RELO_LD64) {

			struct bpf_insn *insns = prog->insns;

			int insn_idx, map_idx;



			insn_idx = prog->reloc_desc[i].insn_idx;

			map_idx = prog->reloc_desc[i].map_idx;
@@ -984,6 +1058,12 @@ bpf_program__relocate(struct bpf_program *prog, struct bpf_object *obj) 
			}

			insns[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;

			insns[insn_idx].imm = obj->maps[map_idx].fd;

		} else {

			err = bpf_program__reloc_text(prog, obj,

						      &prog->reloc_desc[i]);

			if (err)

				return err;

		}

	}



	zfree(&prog->reloc_desc);
@@ -1026,7 +1106,6 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) 
		Elf_Data *data = obj->efile.reloc[i].data;

		int idx = shdr->sh_info;

		struct bpf_program *prog;

		size_t nr_maps = obj->nr_maps;



		if (shdr->sh_type != SHT_REL) {

			pr_warning("internal error at %d\n", __LINE__);
@@ -1040,11 +1119,9 @@ static int bpf_object__collect_reloc(struct bpf_object *obj) 
			return -LIBBPF_ERRNO__RELOC;

		}



		err = bpf_program__collect_reloc(prog, nr_maps,

		err = bpf_program__collect_reloc(prog,

						 shdr, data,

						 obj->efile.symbols,

						 obj->efile.maps_shndx,

						 obj->maps);

						 obj);

		if (err)

			return err;

	}
@@ -1197,6 +1274,8 @@ bpf_object__load_progs(struct bpf_object *obj) 
	int err;



	for (i = 0; i < obj->nr_programs; i++) {

		if (obj->programs[i].idx == obj->efile.text_shndx)

			continue;

		err = bpf_program__load(&obj->programs[i],

					obj->license,

					obj->kern_version);
@@ -1859,7 +1938,7 @@ long libbpf_get_error(const void *ptr) 
int bpf_prog_load(const char *file, enum bpf_prog_type type,

		  struct bpf_object **pobj, int *prog_fd)

{

	struct bpf_program *prog;

	struct bpf_program *prog, *first_prog = NULL;

	struct bpf_object *obj;

	int err;
@@ -1867,12 +1946,7 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type, 
	if (IS_ERR(obj))

		return -ENOENT;



	prog = bpf_program__next(NULL, obj);

	if (!prog) {

		bpf_object__close(obj);

		return -ENOENT;

	}



	bpf_object__for_each_program(prog, obj) {

		/*

		 * If type is not specified, try to guess it based on

		 * section name.
@@ -1886,6 +1960,16 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type, 
		}



		bpf_program__set_type(prog, type);

		if (prog->idx != obj->efile.text_shndx && !first_prog)

			first_prog = prog;

	}



	if (!first_prog) {

		pr_warning("object file doesn't contain bpf program\n");

		bpf_object__close(obj);

		return -ENOENT;

	}



	err = bpf_object__load(obj);

	if (err) {

		bpf_object__close(obj);
@@ -1893,6 +1977,6 @@ int bpf_prog_load(const char *file, enum bpf_prog_type type, 
	}



	*pobj = obj;

	*prog_fd = bpf_program__fd(prog);

	*prog_fd = bpf_program__fd(first_prog);

	return 0;

}

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